Christ has paid the penalty of the law once for all on the cross. According to Paul, it is because the full penalty of the law has been paid, and not at all because the law is to be taken lightly, that the Christian is free from the law.
Acts 9:1-19, and Parallels
Early in life Paul went to Jerusalem, to receive training under Gamaliel, the famous Pharisaic teacher. And in Jerusalem, when he had still not reached middle age, he engaged bitterly in persecution of the Church. He was filled with horror at a blasphemous sect that proclaimed a crucified malefactor to be the promised King of Israel, and that tended, perhaps, to break down the permanent significance of the law. It is a great mistake to suppose that before he was converted Paul was gradually getting nearer to Christianity. On the contrary, he was if anything getting further away, and it was while he was on a mad persecuting expedition that his conversion finally occurred.
The conversion of Paul was different in one important respect from the conversion of ordinary Christians. Ordinary Christians, like Paul, are converted by the Holy Spirit, who is the Spirit of Jesus. But in the case of ordinary Christians human instruments are used — the preaching of the gospel, or godly parents, or the like. In the case of Paul, on the other hand, no such instrument was used, but the Lord Jesus himself appeared to Paul and brought him the gospel. Paul himself says in one of his Epistles that he saw the Lord. I Cor. 9:1; 15:8. It was that fact which made Paul, unlike ordinary Christians, but like Peter and the other apostles, an actual eyewitness to the resurrection of Christ.
A wonderful thing, moreover, was the way in which Jesus appeared to Paul. He might naturally have appeared to him in anger, to condemn him for the persecution of the Church. Instead he appeared in love, to receive him into fellowship and to make him the greatest of the apostles. That was grace — pure grace, pure undeserved favor. It is always a matter of pure grace when a man is saved by the Lord Jesus, but in the case of Paul, the persecutor, the grace was wonderfully plain. Paul never forgot that grace of Christ; he never hated anything so much as the thought that a man can be saved by his own good works, or his own character, or his own obedience to God's commands. The gospel of Paul is a proclamation of the grace of God.